François Hollande's lead over Nicolas Sarkozy is narrowing just two days before France's presidential elections, but the incumbent still has a formidable challenge to overhaul the deficit in time for Sunday's vote.

The last Ipsos poll for French television and Le Monde puts Hollande on 52.5% with Sarkozy closing the gap but still behind on 47.5%. The poll was taken before the dramatic decision by centrist François Bayrou to throw his weight behind Hollande in the second round.

The vast majority of voters appear to have made up their minds, with 92% saying they know who they will vote for, and 82% saying they will definitely turn out.

Though third-placed Marine Le Pen has said she will vote for neither candidate in the second round, 54% of her supporters are lining up behind Sarkozy, compared with 15% for Hollande. Sarkozy is also ahead among supporters of Bayrou, by 38% to 30%. But among supporters of fourth-placed Jean-Luc Mélenchon of the leftwing Front de Gauche, Hollande is ahead by 76%-6%.